<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>伪类</title>
  <style>
    .d1 {
      background-color: aliceblue;
      width: 200px;
      height: 400px;
    }
    .d1:hover{
      background-color: red;
    }
  </style>
</head>
<body>
    <div class="d1">123123</div>
</body>
</html>